1. Field of the Invention
The present invention relates to a method for removing detrimental substances, i.e., nitrogen oxides and organic chlorine compounds such as polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans from a combustion waste gas discharged from an incinerator, and a filter for removing dust and detrimental substances as described above from the above-mentioned combustion waste gas.
2. Related Art Statement
Industrial and household wastes are incinerated in an incinerator, and such wastes often contain chlorine compounds these days. When wastes containing chlorine compounds are incinerated, a combustion waste gas produced in the incinerator and discharged therefrom contains detrimental substances, i.e., nitrogen oxides (NO.sub.x) and organic chlorine compounds such as polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs). Particularly, organic chlorine compounds in the combustion waste gas, though slight in amount, have a very strong toxicity. It is therefore very important for pollution control to remove detrimental nitrogen oxides and also detrimental organic chlorine compounds from a combustion waste gas. Under such circumstances, various methods for removing the above-mentioned detrimental substances from a combustion waste gas have been developed.
Japanese Patent Publication No. 54-29,419 dated Sep. 22, 1979 discloses a method for removing nitrogen oxides from a combustion waste gas, which comprises the steps of:
adding ammonia as a reducing agent to a combustion waste gas; and
causing said combustion waste gas added with said ammonia as the reducing agent to contact with a catalyst for reducing nitrogen oxides to reduce nitrogen oxides contained in said combustion waste gas so as to decompose same, thereby removing said nitrogen oxides from said combustion waste gas (hereinafter referred to as the "prior art 1").
Japanese Patent Provisional Publication No. 63-290,314 dated Nov. 28, 1988 discloses a method for removing organic chlorine compounds from a combustion waste gas, which comprises the steps of:
causing a combustion waste gas to contact, while keeping the temperature of said combustion waste gas within a range of from 300.degree. to 900.degree. C. with a catalyst for oxidizing organic chlorine compounds to oxidize organic chlorine compounds contained in said combustion waste gas so as to decompose same, thereby removing said organic chlorine compounds from said combustion waste gas (hereinafter referred to as the "prior art 2").
Japanese Patent Provisional Publication No. 62-65,721 dated Mar. 25, 1987 discloses a method for removing nitrogen oxides, carbon monoxide, hydrocarbon and organic compounds containing oxygen such as aldehyde from a combustion waste gas, which comprises the steps of:
adding ammonia as a reducing agent to a combustion waste gas;
causing said combustion waste gas added with said ammonia as the reducing agent to contact with a catalyst for reducing nitrogen oxides to reduce nitrogen oxides contained in said combustion waste gas so as to decompose same, thereby removing said nitrogen oxides from said combustion waste gas; and
causing said combustion waste gas, from which said nitrogen oxides have thus been removed, to contact with an oxidizing catalyst comprising platinum and/or palladium to oxidize carbon monoxide, hydrocarbon and organic compounds containing oxygen such as aldehyde contained in said combustion waste gas so as to decompose same, thereby removing said carbon monoxide, said hydrocarbon and said organic compounds containing oxygen such as aldehyde from said combustion waste gas (hereinafter referred to as the "prior art 3").
According to the prior art 1, it is possible to remove only nitrogen oxides from the combustion waste gas. In the prior art 1, however, no regard is paid to the removal of both nitrogen oxides, and organic chlorine compounds such as polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) from the combustion waste gas.
According to the prior art 2, it is possible to remove organic chlorine compounds from the combustion waste gas. Also in the prior art 2, however, no regard is paid to the removal of both nitrogen oxides, and organic chlorine compounds such as polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) from the combustion waste gas.
According to the prior art 3, it is possible to remove nitrogen oxides, carbon monoxide, hydrocarbon and organic compounds containing oxygen such as aldehyde. Also in the prior art 3, however, no regard is paid to the removal of both nitrogen oxides, and organic chlorine compounds such as polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) from the combustion waste gas.
Under such circumstances, there is a strong demand for the development of a method for efficiently removing detrimental substances, i.e., both nitrogen oxides, and organic chlorine compounds such as polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans from a combustion waste gas discharged from an incinerator, but such a method has not as yet been proposed.
A combustion waste gas discharged from an incinerator contains dust in a large quantity in addition to the above-mentioned detrimental substances. It is therefore the usual practice to introduce the combustion waste gas discharged from the incinerator into a dust collector, remove dust from the combustion waste gas by means of a filter provided in the dust collector, and apply to the combustion waste gas, from which dust has thus been removed, a conventional method for removing the above-mentioned detrimental substances from the combustion waste gas, for example, any of the prior arts 1 to 3.
When removing dust and organic chlorine compounds from a combustion waste gas, for example, it is the conventional practice to remove dust from the combustion waste gas by means of a dust collector provided between an incinerator and a stack, and then remove organic chlorine compounds from the combustion waste gas, from which dust has thus been removed, by means of a removing reactor of organic chlorine compounds provided between the dust collector and the stack. In the conventional method, as described above, it is necessary to separately provide the dust collector and the removing reactor of organic chlorine compounds, this inevitably requiring a large site, complicated equipment, and consequently high equipment and running costs.
Under such circumstances, there is a strong demand for the development of a filter, to be attached to a dust collector, which efficiently removes not only dust but also the above-mentioned detrimental substances from a combustion waste gas discharged from an incinerator, and permits achievement of small-scale equipment for the disposal of the combustion waste gas, thereby reducing the equipment and running costs, but such a filter has not as yet been proposed.